A new type of dissolved air flotation apparatus with pipe type reaction and high-efficient dissolved air was studied for improving the treatment efficiency of oil wastewater.The results showed that the oil and SS removal rates of oil wastewater came up to 96% and 85% respectively under the condition of flow 0.50 m³/h,PAC 60 mg/L,reflux ratio 20%,dissolved-air pressure 0.60 MPa and coagulation rate 0.80 m/s,which indicated that the new apparatus had high efficiency and stable operation in treating oil wastewater and would have broad application prospect in oil wastewater and other wastewater treatment field.